Wind farms comprise a plurality of wind turbines which convert wind power into electrical energy using a rotor and a generator connected thereto. The electrical energy passes, via a converter, into a network within the wind farm and, from there, into a supply network via a network feed-in point. A control device is provided at the network feed-in point, which control device detects various measured values, for instance voltages or current strength, at the network feed-in point and thus has an effect on the wind turbines such that setpoint values which are predefined at the network feed-in point, for example in respect of the active power and/or reactive power, are achieved. The setpoint values to be achieved can be automatically calculated by the control device or can be predefined by a superordinate entity, for example the network operator.
A wind farm having a plurality of subnetworks within the wind farm is known from DE 101 36 974. Power can be fed into subregions of the supply network via in each case a network feed-in point from each of the subnetworks within the wind farm. If the subregions of the supply network are connected to one another via a switching device, then the control devices at the network feed-in points are also connected to one another, so that the control of the power fed into the supply network via the respective network feed-in points can be mutually adjusted.
It is known from DE 10 2008 028 573 to provide redundant control devices at a network feed-in point. If a control device fails, a second control device can assume the tasks of the faulty control device.
A disadvantage of said prior art is that, in the event of failure of a network feed-in point, the wind turbines connected to said network feed-in point can no longer output electrical energy to the supply network and must be shut down.